Dear Lifehacker,
After reading how easy it is for someone else to get onto my Wi-Fi network, and, similarly, thinking about how often I let my friends connect to my wireless network, I want to lock down the rest of my network so people connected to it can't go snooping around my computers—or at least secure my most super secret files and folders. What's the best way to go about this?

Dear Insecure,
We hear you. No one's stuff should be rifled through, whether you're protecting something as mundane as photos of you in a swimsuit or more sensitive information like your bank statements and tax returns. If you share your network with friends or neighbors or just want to take extra precautions, these steps can protect your most important data from prying eyes. Most of them, by the way, are similar to the settings tweaks you should make to stay safe on public Wi-Fi networks, because, basically, the concept is the same: If you have any doubt at all when it comes to connecting your computer(s) to others, take a safety-first approach.

Set Permissions on Files or Folders

You can password-protect important files or folders on your computer by editing the permissions settings, which control who can view or edit those items. By editing the permissions settings of a folder you can grant or deny access to specific users on your network (it's based on the computer accounts). Here's how to do it:

In Windows, right-click the folder, go to Properties, and open the Security tab. Then click the Edit button. You can then select a group or user name and choose to deny access to the folder. Someone trying to access it will be required to put in an administrator password.

In Mac, this works similarly. Go to the info properties of the folder and under Sharing & Permissions, you can set users' privilege (read only, read & write, no access).

Also don't forget to set up password protection on your network attached storage or any drives shared over the network on your computers.

Encrypt Your Drive or Folders

For extra security—and a less complex way to protect your files than on an account-by-account basis—, you'll want to protect the really private files on your network using encryption tools. Our favorite encryption utilityTrueCrypt can secure your entire system, a set of folders or files, or even external drives. It's also pretty easy to set up.

The built-in Disk Utility in Mac also is a great tool for protecting folders. Head to Applications > Utilities to find Disk Utility and create a new blank disk image which you can set to 256-bit encryption and add a password. Then drag files or folders onto the new .dmg drive you created to secure them.

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Alternatively, if you have just a few sensitive docs you want to protect, use 7-Zip with its strong AES-256 encryption to zip up those files. Using 7-zip is just a matter of right-clicking to send files or folders to an archive or entering in the password to decrypt the zipped file.

Turn Off File Sharing and Network Discovery

If you're really concerned, look to your system's settings to turn off file and folder sharing, as well as network discovery. Ticking these options off makes your computer practically invisible to other computers on the network (at least to the lay person).

In Windows, this is under Control Panel > Network and Internet > Network and Sharing Center > Advanced Sharing Center. Turn off file sharing, printer sharing, public folder sharing, and network discovery.

In Mac, go to System Preferences > Sharing and uncheck all boxes. Then, under Security & Privacy > Firewall's advanced settings, check "stealth mode" to keep your computer from responding to requests to access it across the network.

Hide your Files

If you don't really need full-blown NSA-grade security, however, another option is to bury your files in hidden dot folders (e.g., ".hidden-folder") or, if you're so inclined, hide the file in an image, PDF, HTML or MP3 file via steganography. Neither are bulletproof, but they can add an extra layer of obscurity.

Enable or Setup a Guest Network

As many readers have pointed out below, if your router hardware supports it, you can set up a separate wireless network altogether for your guests to access, protecting your computers. This separate network can be open (unencrypted) or secured with a password. You can set it up with either a router that supports guest access or by using two wireless routers.

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For some routers, all you have to do is go into the administration panel and select the guest networking option. Select that option and you have a convenient second network that doesn't allow access to anything on your network at all. (Guess access is just one of the features to look for when shopping around for a new router.)

If you have an older router without that option, however, all is not lost. You can just add another wireless router to your existing wireless network for a second wireless network.

For example, I have a wireless router/modem combo given to me by Verizon, to which I've attached a more advanced Netgear router (connecting these two via Ethernet cable and the LAN ports). Because these two routers are on different subnets (the Verizon router/modem has a 192.168.1.X subnet by default and the Netgear has a 10.0.0.X subnet by default) the information sent over each of these individual networks is separated and secured, so one network can be shared with guests and the other used privately.

Setup a Private VPN

If you want to share everything between two or more computers and encrypt everything in transit, you can set up your own private network using software like Hamachi. The VPN, or virtual private network, securely connects your devices and encrypts all the data routed between them. So even if the info is intercepted, it can't be read—making VPN great for people who use unsecured networks or work remotely.